Adams Platinum Oxide

The development of more active and reproducible precious metal catalysts continued in the 1920s when Roger Adams produced his platinum oxide catalyst by the method shown in Table 3.6.  

Since then Adams platinum has been used in the pharmaceutical industry and in small-scale hydrogenation reactions. When industrial processes requiring precious metal catalysts were developed it was not economic to operate with high platinum concentrations. It was, therefore, necessary to reduce costs by supporting small amounts of the metal on a suitable diluent. Supports iiKluded alumina, asbestos, sihca gel, and, most often, activated carbon. Products from these processes have included vitamins, cortisone, and dihydrostreptomycin. 

By 1930 Carleton Elhs, who worked on organic hydrogenation reactions and the chemistry of petroleum derivatives, was able to publish a book that included a literature survey of the recent developments in hydrogenation reactions and catalysts.  

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CATALYTIC REDUCTION WITH ADAMS PLATINUM OXIDE CATALYST... 

Place a solution of 10 -4 g. of benzalacetophenone, m.p. 57° (Section IV,130) in 75 ml. of pure ethyl acetate (Section 11,47,15) in the reaction bottle of the catalytic hydrogenation apparatus and add 0 2 g. of Adams platinum oxide catalyst (for full experimental details, see Section 111,150). Displace the air with hydrogen, and shake the mixture with hydrogen until 0 05 mol is absorbed (10-25 minutes). Filter oflF the platinum, and remove the ethyl acetate by distillation. RecrystaUise the residual benzylacetophenone from about 12 ml. of alcohol. The yield of pure product, m.p. 73°, is 9 g. 

Hydrocinnamic acid may also be prepared by the reduction of cinnamic acid with sodium and alcohol or with sodium amalgam or with hydrogen in the presence of Adams platinum oxide catalyst (Section 111,150) ... 

The Adams platinum oxide catalyst gives satisfactory results in the reduction of ozonidea. 

Palladium catalysts are useful alternatives to Adams platinum oxide catalyst described in Section 111,150. The nearest equivalent to the latter is palladium chloride upon carbon and it can be stored indefinitely the palladium salt is reduced to the metal as required ... 

The well-known Adams platinum oxide can be prepared conveniently by the procedure of Adams et al. (2). Platinum oxides prepared in this way usually contain some traces of sodium, which in certain reactions can have an adverse effect. The sodium can be removed by washing with dilute acid (53). The Nishimuri catalyst (30% Pt, 70% Rh oxides) can be prepared by the same procedure as for platinum oxide or with variations from platinum and rhodium salts (64,65,66). This catalyst has much merit. It is usually most useful when hydrogenolysis is to be avoided (67,85,86). 

B. Diethyl cis-hexahydrophthalate. The reaction is carried out in a low-pressure catalytic hydrogenation apparatus. In a 500-ml. Pyrex centrifuge bottle are placed 0.5 g. of Adams platinum oxide catalyst (Note 5) and 20 ml. of commercial absolute ethanol (Note 6). The bottle is connected to a calibrated low-pressure hydrogen tank and alternately evacuated and filled with hydrogen twice. Hydrogen is then admitted to the system until the pressure is 1-2 atmospheres (15-30 lb.), and the bottle is shaken for 20-30 minutes to reduce the platinum oxide. The shaker is stopped, the bottle is evacuated, and air is admitted. Two hun-... 

Dimethyl cw-hexahydrophthalate also may be prepared by a similar reduction of dimethyl m-A -tetrahydrophthalate. With 0.5 g. of prereduced Adams platinum oxide catalyst, 198 g. (1 mole) of dimethyl m-A -tetrahydrophthalate was reduced to give 196 g. (98%) of dimethyl cw-hexahydrophthalate, b.p. 110-112°/5 mm., Wd 1.4570. 

Adams platinum oxide catalyst is readily prepared from chloroplatinio acid or from ammonium chloroplatinate, and is employed for catalytio hydrogenation at pressures of one atmosphere to several atmospheres and from room temperature to about 90°. Reduction is usually carried out with rectified spirit or absolute alcohol as solvents. In some cases (e.g., the reduction of benzene, toluene, xylene, mesitylene, cymene and diphenyl ), the addition to the absolute alcohol solution of 2-5 per cent, of the volume of rectified spirit which has been saturated with hydrogen chloride increases the effectiveness of the catalyst under these conditions chlorobenzene, bromobenzene, o-, m- and p-bromotoluenes, p-dichloro- and p-dibromo-benzene are reduced completely but the halogens are simultaneously eliminated. Other solvents which are occasionally employed include glacial acetic acid, ethyl acetate, ethyl acetate with 17 per cent, acetic acid or 8 per cent, of alcohol. In the actual hydrogenation the platinum oxide Pt02,H20 is first reduced to an active form of finely-divided platinum, which is the real catalyst allowance must be made for the consumption of hydrogen in the process. 

Catalytic reduction, with Adams platinum oxide catalyst, 470 with copper-chromium oxide, 873 with Raney nickel, 566 Cation exchange resin, for esterification, 381, 387, 388 Cellosolve, 170, 265, 444 butyl, 170, 444 methyl, 170, 444 Cellulose, 458 ... 

Then, as described in US Patent 3,053,845, one hundred grams (0.278 mol) of 2-oxo-3-(N,N-diethylcarboxamido)-9,10-dimethoxy-l,2,3,4,6,7-hexahydro-llb-H-benzopyridocoline was dissolved in 1,500 ml of hot methanol and the resulting solution was allowed to cool to room temperature. After removal of all the dissolved oxygen therein by saturation of the solution with dry nitrogen, 5.0 grams of Adams platinum oxide catalyst was introduced into the system in one portion while still maintaining same under a nitrogen atmosphere. 

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